How do you stream MP3s from Windows Media Server over HTTP to the widest variety of audio clients?

A sample MP3 file streams successfully from Windows Media Server (v9 on w2k3) over http:// to Windows Media Player (v9) but fails to stream to Real Player (v8) or WinAmp (v5.093). It plays successfully in Real and WindAmp when played locally, so it is the streaming that is not working. Strangely, streaming over mms:// to WinAmp also worked.

WinAmp displays: "Error syncing to mpeg"
Real Player displays: "MPEG by Bitcasting: File Format cannot find MPEG file header. This may not be an MPEG file."

The MP3 file was created with Audacity (v1.2.3) using lame_enc.dll. File
properties are:
Bit rate: 128 kbps
Channels: 1
Sample Rate: 44kHz

What do I need to do to stream MP3s over HTTP to Real Player & WinAmp?